Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

A trough filter integrated with a thermoelectric generator includes
annular filter modules having a support structure at its inner
circumference, a filter element, and a support structure at its outer
circumference. The filter elements may be configured to form troughs. An
annular exhaust gas outlet channel or gas inlet channel may be formed
between filter modules. The thermoelectric generator may be positioned in
the exhaust gas outlet or inlet channel. A vehicle includes the trough
filter integrated with a thermoelectric generator downstream from an
internal combustion engine. A method of treating exhaust gas uses a
trough filter with an integrated thermoelectric generator.

Claims:

1. A trough filter or substrate integrated with a thermoelectric
generator, wherein: the trough filter comprises: a first annular filter
module comprising a first support structure at its inner circumference, a
filter element, and a second support structure at its outer
circumference; and a second annular filter module comprising a third
support structure at its inner circumference, a filter element, and a
fourth support structure at its outer circumference, wherein the filter
elements are configured to form troughs, the first and second filter
modules are concentric, an inner diameter of the second filter module is
larger than an outer diameter of the first filter module, and an annular
exhaust gas outlet or inlet channel is formed between the first filter
module and the second filter module by providing a gap between the second
support structure and the third support structure; and the thermoelectric
generator is positioned in the exhaust gas outlet or inlet channel and
the thermoelectric generator comprises: a first heat exchanger connected
to the second support structure; a second heat exchanger; a first
thermoelectric module positioned between the first heat exchanger and the
second heat exchanger; a third heat exchanger connected to the third
support structure; and a second thermoelectric module positioned between
the second heat exchanger and the third heat exchanger.

2. The trough filter or substrate of claim 1, wherein at least one of the
filter elements comprises a porous material.

3. The trough filter or substrate of claim 1, wherein at least one of the
filter elements comprises a catalyst.

4. The trough filter or substrate of claim 1, wherein the trough filter
or substrate comprises a member selected from the group consisting of
cordierite, silicon carbide, silicon nitride, aluminum titanate,
eucryptite, mullite, calcium aluminate, zirconium phosphate, and
spodumene.

5. The trough filter or substrate of claim 1, wherein the first heat
exchanger is connected to the second support structure by direct,
physical contact, and the third heat exchanger is connected to the third
support structure by direct, physical contact.

6. The trough filter or substrate of claim 1, wherein the first heat
exchanger is connected to the second support structure via a thermal
transfer medium, and the third heat exchanger is connected to the third
support structure via a thermal transfer medium.

7. The trough filter or substrate of claim 1, wherein the thermoelectric
generator is exposed to a fluid that flows through the trough filter.

8. The trough filter or substrate of claim 1, wherein the thermoelectric
generator is not exposed to a fluid that flows through the trough filter.

9. The trough filter or substrate of claim 1 further comprising a cooling
circuit that is in thermal contact with the thermoelectric generator.

10. The trough filter or substrate of claim 1, wherein the thermoelectric
generator is configured to cool inner dimensions of the trough filter.

11. The trough filter or substrate of claim 1 further comprising at least
one temperature sensor configured to measure a temperature of inner
dimensions of the trough filter.

12. The trough filter or substrate of claim 1, wherein the thermoelectric
generator comprises a plurality of n-type components and a plurality of
p-type components.

13. The trough filter or substrate of claim 12, wherein the n-type and
p-type components are alternating n-type rings and p-type rings.

14. A vehicle comprising an internal combustion engine, a trough filter
or substrate integrated with a thermoelectric generator, and an exhaust
gas outlet or inlet running from the internal combustion engine through
the trough filter, wherein: the trough filter or substrate integrated
with the thermoelectric generator is positioned downstream from an
exhaust manifold of the internal combustion engine; the trough filter or
substrate separates particulate from the exhaust gas; the trough filter
or substrate comprises: a first annular filter module comprising a first
support structure at its inner circumference, a filter element, and a
second support structure at its outer circumference; and a second annular
filter module comprising a third support structure at its inner
circumference, a filter element, and a fourth support structure at its
outer circumference, wherein the filter elements are configured to form
troughs, the first and second filter modules are concentric, an inner
diameter of the second filter module is larger than an outer diameter of
the first filter module, and an annular exhaust gas outlet or inlet
channel is formed between the first filter module and the second filter
module by providing a gap between the second support structure and the
third support structure; and the thermoelectric generator is positioned
in the exhaust gas outlet or inlet channel and the thermoelectric
generator comprises: a first heat exchanger connected to the second
support structure; a second heat exchanger; a first thermoelectric module
positioned between the first heat exchanger and the second heat
exchanger; a third heat exchanger connected to the third support
structure; and a second thermoelectric module positioned between the
second heat exchanger and the third heat exchanger.

15. The vehicle of claim 14, wherein the trough filter or substrate is a
gasoline particulate filter.

16. The vehicle of claim 15 further comprising an after-treatment system
that comprises: the gasoline particulate filter; and at least two
three-way catalyst substrates.

17. The vehicle of claim 16, wherein the gasoline particulate filter is
positioned between the two three-way catalyst substrates.

18. The vehicle of claim 14, wherein the trough filter or substrate is a
diesel particulate filter.

19. The vehicle of claim 18 further comprising an after-treatment system
that comprises: the diesel particulate filter; a diesel oxidation
catalyst substrate; a selective catalytic reduction substrate; and an
ammonia slip catalyst substrate or a lean NOx trap.

20. The vehicle of claim 19, wherein the diesel particulate filter is
positioned between the diesel oxidation catalyst substrate and the
selective catalytic reduction substrate.

21. A method for converting heat into energy, the method comprising:
flowing hot gas through a trough filter or substrate, wherein the trough
filter or substrate comprises: a first annular filter module comprising a
first support structure at its inner circumference, a filter element, and
a second support structure at its outer circumference; and a second
annular filter module comprising a third support structure at its inner
circumference, a filter element, and a fourth support structure at its
outer circumference, wherein the filter elements are configured to form
troughs, the first and second filter modules are concentric, an inner
diameter of the second filter module is larger than an outer diameter of
the first filter module, and an annular exhaust gas outlet or inlet
channel is formed between the first filter module and the second filter
module by providing a gap between the second support structure and the
third support structure; and exchanging heat between the flowing exhaust
gas and at least one thermoelectric generator that is positioned in the
exhaust gas outlet or inlet channel, wherein the thermoelectric generator
comprises: a first heat exchanger connected to the second support
structure; a second heat exchanger; a first thermoelectric module
positioned between the first heat exchanger and the second heat
exchanger; a third heat exchanger connected to the third support
structure; and a second thermoelectric module positioned between the
second heat exchanger and the third heat exchanger.

22. The method of claim 21, further comprising reacting the exhaust gas
with a catalyst during the flowing through the trough filter or
substrate.

23. The method of claim 21, further comprising filtering the exhaust gas
during the flowing through the trough filter or substrate.

24. The method of claim 21, further comprising flowing a coolant through
a cooling circuit that is in thermal communication with the
thermoelectric generator.

Description:

BACKGROUND

[0001] 1. Field

[0002] The present disclosure relates to an exhaust gas after-treatment
unit such as a diesel or gas particulate filter or catalyzed substrate
with a thermoelectric generator integrated therein. The exhaust gas
after-treatment unit may be included in the exhaust system of a vehicle.

[0003] 2. Technical Background

[0004] Thermoelectric generators may be used in vehicles to convert heat
from exhaust gas into electrical power, which may be used in other
systems of the vehicle or stored in a battery. Various locations and
designs of thermoelectric generators have been used. However,
conventional designs of thermoelectric generators may be difficult to
place in an exhaust system due to size constraints, increased resulting
mass in the exhaust system and resulting back-pressure issues.
Accordingly, there is a need for a thermoelectric generator that may be
efficiently integrated into the exhaust system of a vehicle without
creating an undue increase in back-pressure.

BRIEF SUMMARY

[0005] The concepts of the present disclosure are generally applicable to
thermoelectric generators. In accordance with one embodiment of the
present disclosure, a trough filter integrated with a thermoelectric
generator may include several annular filter modules, such as a first
annular filter module comprising a first support structure at its inner
circumference, a filter element, and a second support structure at its
outer circumference. The trough filter may also include a second annular
filter module comprising a third support structure at its inner
circumference, a filter element, and a fourth support structure at its
outer circumference. The filter elements may be configured to form
troughs, and the first and second filter modules may be concentric. An
inner diameter of the second filter module may be larger than an outer
diameter of the first filter module, such that an annular exhaust gas
outlet channel may be formed between the first filter module and the
second filter module, i.e., by way of a gap between the second support
structure and the third support structure. The thermoelectric generator
may be positioned in the exhaust gas channel. The exhaust gas channel may
be a gas inlet channel or a gas outlet channel. The thermoelectric
generator may include a first heat exchanger connected to the second
support structure, a second heat exchanger, a first thermoelectric module
positioned between the first heat exchanger and the second heat
exchanger, a third heat exchanger connected to the third support
structure, and a second thermoelectric module positioned between the
second heat exchanger and the third heat exchanger.

[0006] In accordance with another embodiment of the present disclosure, a
vehicle may include an internal combustion engine, and a trough filter
integrated with a thermoelectric generator as described above. The
vehicle may further comprise an exhaust gas outlet running from the
internal combustion engine through the trough filter. The trough filter
may be positioned downstream of the internal combustion engine.

[0007] In accordance with an embodiment of the present disclosure, a
method for converting heat into energy may include flowing hot gas
through a trough filter as described above. The method may further
include exchanging heat between the flowing exhaust gas and at least one
thermoelectric generator as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The following detailed description of specific embodiments of the
present disclosure can be best understood when read in conjunction with
the following drawings, where like structure is indicated with like
reference numerals and in which:

[0009] FIG. 1 is a schematic showing exemplary types and exemplary orders
of after-treatment devices in a gasoline engine;

[0010] FIG. 2 is a schematic showing exemplary types and exemplary orders
of after-treatment devices in a diesel engine;

[0011] FIG. 3A is a schematic of a thermoelectric element with p- and
n-type legs, that produces electrical power in a temperature gradient;

[0012] FIG. 3B is a plot of thermoelectric efficiency versus the Figure of
Merit (ZT) for two different hot-side temperatures and one fixed
cold-side temperature;

[0014] FIG. 5A is a schematic showing the temperature distribution (T)
across the transverse direction (r) of honeycomb (HF) and trough (TF)
substrates or filters during normal operation;

[0015] FIG. 5B is a schematic showing the temperature distribution (T)
across the transverse direction (r) of honeycomb (HF) and trough (TF)
substrates or filters during regeneration.

[0016] FIG. 6 is a schematic showing an after-treatment device;

[0017] FIG. 7 is a schematic cross section of a trough filter including an
integrated thermoelectric generator that includes the thermoelectric
device and a heat exchanger according to embodiments of the present
disclosure;

[0018] FIG. 8 shows an example embodiment of thermoelectric generator
element patterns according to embodiments of the present disclosure;

[0019] FIGS. 9A and 9B are schematics showing electrical interconnections
among a plurality of thermoelectric generator devices; and

[0020] FIG. 10 is a schematic showing a fitting configuration for an
after-treatment device having an integrated thermoelectric generator.

DETAILED DESCRIPTION

[0021] According to an exemplary embodiment, a trough filter with an
integrated thermoelectric generator generally may comprise multiple
concentric filter elements and an annular exhaust gas outlet channel
located between one or more of the elements, along a central axis of the
generator or at a peripheral channel. The thermoelectric generator may be
positioned in thermal communication with the annular exhaust gas inlet or
outlet channel. The thermoelectric generator may include hot-side heat
exchangers, cold-side heat exchangers, and thermoelectric modules. The
trough filter with an integrated thermoelectric generator may be included
in an after-treatment system of a vehicle.

[0022] By incorporating a thermoelectric module in thermal communication
with the annular exhaust gas channel, greater conversion efficiencies may
be achieved. In addition, placement of the thermoelectric module in
thermal communication with the annular exhaust gas channel may
advantageously promote homogenization of the overall after-treatment
device temperature during its operation, particularly an after-treatment
device constructed with low thermal conductivity materials, thereby also
significantly widening the operation window of the after-treatment
system.

[0023] In vehicles with a gasoline engine, for example, exhaust gas may
pass through one or more three-way catalyst (TWC) substrates. As
illustrated schematically in FIG. 1, gasoline after-treatment systems may
include a TWC substrate 20 that may be close-coupled to an engine 21,
along with another underbody TWC substrate 20 further downstream. A
gasoline particulate filter (GPF) substrate 22 may also be provided. A
GPF may be functionalized with a de-NOx SCR catalyst and/or an oxidation
catalyst (e.g., CO oxidation catalyst). In embodiments, during operation
of engine 21, air may enter via an air intake 23, may be compressed by a
turbocharger 24, cooled by an inter-cooler 25, and passed through intake
valves 26 into the engine's cylinders. After adding and igniting fuel,
exhaust gas may emerge from exhaust valves 27, may be combined in an
exhaust manifold 28, used to spin the turbocharger 24 (if present), and
passes through the TWCs 20 and GPF 22.

[0024] The thermal mass of the TWC 20 and/or the GPF 22 may allow heat
storage from exhaust gas passing through an exhaust system, and engine
coolant may be, for example, routed through the after-treatment system
from a radiator 29 via a coolant pipe 30 to act as a heat sink. In some
embodiments, the GPF 22 may be a trough filter, such as the trough filter
described in more detail below.

[0025] Referring now to FIG. 2, during operation of a diesel engine 31,
part of the exhaust gas that emerges from the exhaust manifold 28 is
directed to the intake valves 26 (i.e., through an exhaust gas
recirculation loop (EGR) 32, which may pass through an EGR cooler 36).
The remaining exhaust gas may pass through a series of after-treatment
elements. Catalyst substrates may include, for example, a diesel
oxidation catalyst (DOC) substrate 33, a selective catalytic reduction
(SCR) catalyst substrate 34, and an ammonia slip catalyst substrate 35.
In various exemplary embodiments, a diesel vehicle may also substitute a
lean NOx trap (LNT) for the SCR and ammonia slip catalyst substrates.
Catalyst substrates may often be composed of a cellular ceramic or metal,
which may be coated with the catalytic material.

[0026] In embodiments, the diesel engine 31 may also include a diesel
particulate filter (DPF) substrate 37. The DPF substrate 37 may be made
using various porous cellular ceramic substrates whose ends are plugged
in a checkerboard fashion, or by using a partial flow filter made, for
example, of corrugated metal sheets. In some embodiments, the DPF
substrate 37 may be a trough filter, such as the trough filter described
in more detail below. The DPF may be functionalized with de-NOx SCR
catalyst and/or DOC catalyst.

[0027] As with the gasoline engine above, the thermal mass of the catalyst
substrates 33, 34 and 35 and/or the DPF substrate 37 may store heat from
exhaust gas passing through the after-treatment system and serve as a
(modulated, and by the hot exhaust gas continuously replenished) heat
supply. Engine coolant may be, for example, routed through the
after-treatment system from a radiator 29 via a coolant pipe 30 to act as
a heat sink.

[0028] As used herein, a "substrate" or an "after-treatment substrate"
includes, but is not limited to, catalytic substrates and particulate
filters that are intended to remove pollutants from engine exhaust gas.
Substrates may include, for example, a porous body made from various
metal and ceramic materials, including, but not limited to, cordierite,
silicon carbide (SiC), silicon nitride, aluminum titanate (AT),
eucryptite, mullite, calcium aluminate, zirconium phosphate and
spodumene. A "catalyst substrate" may include, for example, a porous
body, such as a TWC, DOC or SCR, which may be infiltrated with a catalyst
that assists a chemical reaction to reduce or eliminate the concentration
of various pollutants within the exhaust gas (e.g., carbon monoxide,
nitrogen oxides, sulfur oxide, and hydrocarbons). A "particulate filter"
may include, for example, a porous body, such as a GPF or DPF substrate,
which traps and therefore reduces particulate matter within the exhaust
stream (e.g., soot and ash). GPF and DPF can be in addition
functionalized with in-pore or on-wall SCR and/or DOC catalyst coatings.

[0029] Various substrates of the present disclosure are based on a trough
design and may have, within that type of design, any shape or geometry
suitable for a particular application, as well as a variety of
configurations and designs, including, but not limited to, a flow-through
structure, a wall-flow structure, or any combination thereof (e.g., a
partial-flow structure). Exemplary flow-through structures include, for
example, any structure comprising channels or porous networks or other
passages that are open at both ends and permit the flow of exhaust gas
through the passages from one end to an opposite end. Exemplary wall-flow
structures include, for example, any structure comprising channels or
porous networks or other passages with individual passages open and
plugged at opposite ends of the structure, thereby enhancing gas flow
through the channel walls as the exhaust gas flows from one end to the
other. Exemplary partial-flow structures include, for example, any
structure that is partially flow-through and partially wall-flow.

[0030] In various exemplary embodiments, the substrates, including those
substrate structures described above, may be monolithic structures.
Various exemplary embodiments of the present disclosure contemplate
utilizing the geometry of a trough configuration due to its high surface
area per unit volume for deposition of soot and ash. The channels of a
trough structure may have virtually any shape; there could be one ring of
crowns or several; the interspacing between the crowns can be varied and
the flow directions between adjacent crowns can be in the same direction
or in counter flow direction. Similarly, a trough-based structure may be
configured as either a flow-through structure, a wall-flow structure, or
a partial-flow structure.

[0031] To recover electricity from waste heat, such as exhaust heat
passing through an after-treatment system as shown and described above in
FIGS. 1 and 2, the present disclosure contemplates integrating various
high-temperature thermoelectric materials within after-treatment
substrates. Suitable thermoelectric materials may generally produce a
large thermopower when exposed to a temperature gradient. Suitable
materials, for example, may exhibit a strong dependency of their carrier
concentration on temperature, have high carrier mobility, and low thermal
conductivity. Example materials, which may recover a large fraction of
heat energy, may have a large Figure of Merit (ZT), defined as
ZT=T*S2*(σ/k), wherein T is temperature (in Kelvin), S is the
Seebeck coefficient or thermopower (in V/m), σ is the electric
conductivity (in Siemens/m), and K is the thermal conductivity (in W/mK).
The Seebeck voltage describes the potential difference that is
established across a material exposed to a temperature gradient. The
Seebeck coefficient may be obtained by extrapolating the Seebeck voltage
to a vanishing temperature gradient. Depending on the majority carrier
type in the material, the Seebeck coefficient may be positive or
negative.

[0032] As illustrated with reference to FIG. 3A, an exemplary
thermoelectric generation element (e.g., that includes interconnected
n-type and p-type semi-conductors) may be a primary component of a
thermoelectric generator. A thermoelectric generation couple is built,
for example, of an assembly of interconnected p-type legs and n-type legs
composed of p-type and n-type thermoelectric materials (e.g., n-type and
p-type semi-conductors). As shown in FIG. 3A, when the thermoelectric
generation couple is exposed to a heat source H and a heat sink C that
create a temperature gradient ΔT across the thermoelectric
generation couple, a current I flows clockwise around the circuit and
through resistor R. A plot of the efficiency of converting heat into
electricity as a function of the Figure of Merit ZT is illustrated in
FIG. 3A. As shown in FIG. 3A, for a material having a ZT value of about
1.5, the conversion efficiency is about 10% for a temperature gradient of
about 250 K (i.e., T.sub.hot-T.sub.cold=550 K-300 K=250 K) and about 20%
for a temperature gradient of about 550 K (i.e., T.sub.hot-T.sub.cold=850
K-300 K=550 K).

[0033] Various shapes and arrangements of thermoelectric legs have been
proposed for integrating thermoelectric materials and components into a
thermoelectric generator. For example, one exemplary thermoelectric
generation module is illustrated in FIG. 4. As shown in FIG. 4, a
thermoelectric module 60 may be built between plates 63 and 65,
respectively located on a hot side H and cold side C of the module 60
(e.g., as respectively shown by arrows H and C, heat may be absorbed
through the top surface of plate 63 and may be ejected through the bottom
surface of plate 65). Plates 63 and 65 may, thereby, act respectively as
the heat source and heat sink for the module 60. Alternating p-type legs
and n-type legs 61 are interconnected in series by metal interconnects 62
on both the hot and cold sides of the module 60, so that the total
voltage of the module 60 is made available at end leads 64. Instead of
the simple plates 63 and 65 shown in FIG. 4, in embodiments a
thermoelectric generator may generally contain efficient heat exchangers
that promote efficient heat exchange between the hot and cold sources.

[0034] As above, in various exemplary embodiments, a substrate (e.g., a
catalytic substrate or particulate filter substrate) may comprise a
variety of materials, including materials having a relatively high
thermal conductivity and/or materials having a relatively low thermal
conductivity. In embodiments, a substrate may comprise a metallic
material having a thermal conductivity in the range of about 20 W/mK to
about 25 W/mK. In additional embodiments, a substrate may comprise a
ceramic material having a thermal conductivity in the range of about 0.5
W/mK to about 20 W/mK. In other embodiments, the substrate may also
include a trough structure, wherein the overall thermal conductivity is
reduced compared to the bulk dense material conductivity. Compared to
honeycomb filters with a main axial gas flow component and negligible
radial gas flow component, radial trough and multicrown designs enable a
strong radial gas flow component, which makes the temperature
distribution in the radial direction homogeneous and allows it to
redistribute and equilibrate heat in the radial direction. While radial
heat flux in a honeycomb is mainly provided by heat conduction through
the material walls, the wall thickness and wall material restrict radial
heat transport and render such a design inefficient for heat extraction.
The trough filter design, on the other hand, with its strong radial gas
flow component, offers significantly-improved heat transport in the
radial direction, which facilitates the use of low thermal conductivity,
high porosity oxide ceramic materials and thin wall configurations in
devices capable of efficient heat extraction from exhaust gas.

[0035] The temperature distribution within a substrate (e.g., a catalytic
substrate or particulate filter substrate) may be a function of a number
of parameters. For catalytic substrates, the substrate temperature (and
temperature profile) may be a function of the type of engine, the type of
fuel, the configuration of the after-treatment system, and various other
factors. As depicted in FIG. 5A, the temperature distribution profile of
a trough substrate or filter (TF) design may be quite homogenous during
normal operation compared to the temperature distribution profile of a
honeycomb substrate or filter (HF) where the temperature could be several
hundred degrees cooler at the periphery compared to the core. In FIGS. 5A
and 5B, T indicates temperature and r indicates a transverse distance in
the temperature distribution profile. For efficient operation of the
catalytic substrate, desired operational parameters include a
substantially homogeneous temperature distribution across the substrate,
flow homogeneity, and fast light off. The transverse (e.g., radial for
the substrate configuration of FIG. 5A) temperature gradient of a
honeycomb structure may therefore result in a less efficient use of the
catalyst in the outer, colder periphery of the substrate in the case of a
catalytic substrate, or lead to overheating of the catalyst and substrate
compared to the needed operation temperature. A trough design substrate
(TF) may offer a much more homogeneous radial temperature distribution,
as shown in FIG. 5A, and overcome the disadvantages associated with the
honeycomb substrate's (HF) low radial thermal flow.

[0036] In an un-catalyzed particulate filter substrate, such as for
example a DPF substrate or a GPF substrate, where the temperature may
typically be a function of the location of the filter within the exhaust
system, the average substrate temperature may be less than the average
catalytic substrate temperature. A DPF substrate, for example, may
operate in two principal regimes, a normal operating regime (i.e., a base
temperature for either catalyzed or un-catalyzed filters as shown in FIG.
5A) and a regeneration regime (as shown in FIG. 5B). During filter
regeneration, temperatures may peak due to an exothermal soot oxidation
reaction, for example. For honeycomb filters (HF), due to the low thermal
conduction in the radial filter direction, the filter's core temperature
may be several hundred degrees higher than the temperature at the
periphery, and result in a strong radial temperature gradient.
Trough-based filters (TF) have a strong radial gas flow component and
therefore produce only moderate temperature increase during regeneration.
Thus, as shown in FIG. 5B, the overall temperature gradient remains very
homogeneous over the regeneration period and allows use of the trough
filter as a very constant heat source. In contrast, localized high peak
temperatures occur during regeneration of DPF with a honeycomb design.
These temperature peaks limit the DPF operation range and may require a
bypass valve that avoids conducting the hot gas through the TEG if the
peak temperature is higher than the thermoelectric material, or higher
than any TEG component material stability limit. The trough design DPF
may offer the advantage of not needing such a by-pass because the
temperature is more homogeneous compared to a honeycomb filter, as shown
in FIG. 5B, and more heat energy can be captured without by the TEG
without difficulty. For these same reasons, trough filters also allow use
of thermoelectric materials that are efficient at low temperature, but
have limited temperature stability.

[0037] Transverse temperature gradients in both honeycomb catalytic
substrates and honeycomb particulate filters may, therefore, limit the
operational window of low thermal conductivity filters. One approach to
decreasing the temperature gradient is to use higher thermal conductivity
materials for the substrate or filter. In accordance with embodiments of
the present disclosure, the radial temperature gradient in a substrate or
filter may also be decreased by using a trough-based substrate or filter
design with a strong radial gas flow component. Integrating one or more
thermoelectric generation elements within the multicrown trough structure
may allow strongly enhanced heat extraction at a very homogeneous radial
temperature and thus allow more efficient waste heat recovery within the
vehicle.

[0038] As illustrated in FIG. 6, an after-treatment device 100 may
comprise a substrate 106 having a first end 101, a second end 102, and an
outermost lateral dimension 103, defining an interior volume 104. As used
herein the term "interior volume" refers to the volume bounded by the
outermost lateral dimension. As explained above, when placed within an
after-treatment system, the substrate 106 may be configured to flow
exhaust gas through the interior volume 104 from the first end 101 to the
second end 102. In embodiments, for example, the substrate is a structure
comprising a plurality of trough channels 115 that permit the flow of
exhaust gas through the trough channels 115 from the first end 101 to the
second end 102. In an exemplary embodiment, the substrate comprising
channels has a through-based design; however, the channels may have a
variety of arrangements and configurations (e.g., cross-sections) without
departing from the scope of this disclosure.

[0039] Referring now to FIG. 7, in embodiments, an after-treatment device
may be a filter 1000, such as a radial-flow trough filter. The trough
filter may have any number of concentric, annular filter modules (e.g.,
1010 and 1020) suitable for the desired size and desired use of the
filter. For example, the filter may have at least 2 concentric filter
modules, such as 3, 4, 5, 6, 7, or more concentric filter modules. The
diameters of the concentric filter modules may increase as their distance
from the center axis of the radial flow filter increases. Accordingly,
the outer diameter 1011 of each concentric filter module may be less than
the inner diameter 1021 of concentric filter modules that are further
from the central axis of the radial flow filter. In embodiments, an
annular gas channel (not shown) may be positioned between adjacent filter
modules (such as, for example, between filter elements 1010 and 1020).
The annular gas channel may be formed by allowing a gap to exist between
adjacent filter modules. The number of annular gas channels is not
particularly limited, and may be modified according to the design
parameters of the system. However, in embodiments, the number of annular
gas channels satisfies the following relationship: G≦n-1, where G
represents the number of annular gas channels and n represents the number
of filter modules in the radial flow filter.

[0040] In embodiments, the filter modules of the radial flow filter may
comprise a first support structure at its inner circumference, a second
support structure at its outer circumference, and a filter element
positioned between the first support structure and the second support
structure. The filter element may be positioned between the first support
structure and the second support structure such that the filter element
divides the filter module into a gas inlet and a gas outlet. The filter
element may be porous and may allow gas to pass from the inlet side of
the filter module through the porous filter element and into the outlet
side of the filter module. As the gas passes through the porous filter
element, particulates may be removed from the gas, thereby providing a
clean gas stream to exit the filter module through the outlet side. To
increase the surface area of the filter element in the filter module, the
filter element may be configured in various geometric patterns. For
example, in embodiments, the filter element may be configured to have a
sinuous shape, thereby creating inlet troughs and outlet troughs having a
sinuous shape. It should be understood that other geometries may be used
to increase the surface area of the filter element by forming troughs
within the filter module. The troughs in the trough filters and
substrates may have different trough wall thickness, different geometry
and different radial and circular interspacing. The support structures
and the filter element of the filter module may be made of the same or
different materials. In embodiments, the support structures and the
filter element of the filter module may comprise a catalyst, particulate
filter material, or thermoconductive materials.

[0041] According to embodiments, a thermoelectric generator 1040 may be
positioned in thermal communication with any annular exhaust gas inlet or
outlet channel. For example, a thermoelectric generator 1040 may be
positioned between and connected to two adjacent filter elements 1010 and
1020 and/or in the annular exhaust gas inlet or outlet channel. In some
embodiments, the thermoelectric generator 1040 connected to the adjacent
filter elements 1010 and 1020 by direct, physical contact. In other
embodiments, the thermoelectric generator 1040 may be connected to the
adjacent filter elements 1010 and 1020 via a thermal transfer medium or
an adhesive layer. The thermoelectric generator may include a cold-side
heat exchanger 1050, thermoelectric modules 1070, and hot-side heat
exchangers 1060. As shown in FIG. 7, the cold-side heat exchanger 1050
may be connected to the thermoelectric modules 1070. Each hot-side heat
exchanger 1060 may be connected to a thermoelectric module 1070. It
should be recognized that the cold-side heat exchanger 1050, the
thermoelectric modules 1070, and the hot-side heat exchangers 1060 may be
connected to each other by any mechanism such as, for example, via
direct, physical contact, via a thermal transfer medium, or via an
adhesive layer. The thermal transfer medium may be formed from any type
of conforming, thermally conductive substance. The thermal transfer
medium may serve, for example, to conform to the surfaces of the
thermoelectric module 1060 and the cold-side and hot-side heat exchangers
1050 and 1060, respectively, to effectively enhance thermal transfer from
the heat source or cooling source to the thermoelectric generation
module. Suitable thermal transfer materials may comprise materials having
a low electrical conductivity and a high thermal conductivity, including,
for example, metallic foams, nets, and metal-ceramics. It should also be
recognized that the above configuration may be repeated as many times as
desired.

[0042] In embodiments, the thermoelectric generator may be separated from
the filter module by a thin, pliable ceramic with high thermal
conductivity, such as alumina, mullite, aluminosilicate, aluminum
titanate, or other thin and fibrous ceramic paper. These materials may
allow easy heat transfer and mounting of the thermoelectric generator to
the filter element. In further embodiments, the hot-side heat exchanger
1060 and the cold-side heat exchanger 1050 may be made of any known and
suitable material. For example, in embodiments, the cold-side and
hot-side heat exchangers may comprise aluminum, or other metallic cold
side heat exchanger materials, and/or ceramics, such as SiC, SiAlON, or
others, depending on the hot side temperature.

[0043] According to embodiments, the thermoelectric module may include a
stack of alternating n-type and p-type rings. As shown in FIG. 8, a
thermoelectric generator 105 may comprise a stack of n-type and p-type
rings of small or large diameter, depending on the diameter of the
interspace in the trough filter or substrate where they are introduced,
although it should be recognized that other configurations of n-type and
p-type material may be used in accordance with various embodiments of
this disclosure or the claims. The n-type rings and p-type rings may be
separated from each other. Suitable separating layers may be made, for
example, from a low thermal conductivity, low electrical conductivity
material, such as, for example, a ceramic or glass-ceramic foam, coating
or interlayer.

[0044] As shown in FIGS. 9A and 9B, an electrically insulating heat
transfer layer 310 (i.e., a thermal transfer medium) may separate the
thermoelectric generation elements 309 from the hot-side heat exchanger
1060, and an electrically insulating layer 311 may separate the
thermoelectric generation elements 309 from the cold-side heat exchanger
1050. In embodiments, for example, the insulating layers 310 and 311 may
be patterned to also separate current collectors 323 on one or both of
the hot side and cold side. The current flowing through the current
collectors 323 is depicted by the arrow and reference label I in FIGS. 9A
and 9B. An air, gas, or vacuum space 322 may separate the n-type
components 320 from the p-type components 321. As shown in FIG. 9A, in
various embodiments, the space 322 may be lined with an electrically
insulating material (i.e., insulating layers 310 and 311 are contiguous).
Alternatively, as shown in FIG. 9B, in various additional embodiments,
the current collectors 323 may be coated with an electrical insulating
material (i.e., insulating layers 310 and 311 are not contiguous and
match the dimensions of the respective current collectors 323). In
particulate filter substrate embodiments, lining spaces 322 with an
electrically insulating material (FIG. 9A) that is also impervious to
particulates, may improve the thermoelectric generator function. Such a
configuration, for example, may prevent conducting particulates contained
in the exhaust gas from gathering immediately adjacent to the
thermoelectric generation elements (which could burn during a
regeneration event) and possibly create short-circuits between the
thermoelectric generation elements or current collectors, and/or cause
chemical and/or thermal harm to the thermoelectric generation elements.

[0045] In embodiments, the current collectors 323 may have various
configurations and may be formed from various conductive materials
including, for example, metals, alloys, conductive oxides and/or other
conductive ceramics. Furthermore, the thermoelectric generation elements
309 may have various shapes, configurations, and/or patterns and be
formed from various thermoelectric materials, including, for example,
skutterudite-based thermoelectric materials, lead telluride, silicides,
silicon-germanium alloys, etc., and that the configuration and material
used for the thermoelectric generation elements 309 may be chosen as
desired based on thermal efficiency (i.e., ZT value), cost, and other
such factors.

[0046] As noted previously with respect to FIGS. 5A and 5B, a trough
substrate or filter may demonstrate only a slightly higher temperature in
its core than at its periphery. Such radial transverse thermal gradients
may introduce stress within a substrate and limit its thermo-mechanical
durability and operation window. Accordingly, in embodiments, the
temperature gradients across the trough substrate or filter and, hence,
the thermally-generated stress, in a TEG operation mode may be used to
reduce temperature gradients across the substrate or filter and enhance
the durability by locating one or more thermoelectric generation elements
and/or coolant flow in the hottest region of the substrate. In such a
configuration, the cooling effect of the cooling circuit (i.e., the heat
sink) may reduce the core temperatures and could be used via a smart
control based on temperature feedback to enhance the temperature
homogeneity across the substrate. In another operation example, and
referring to FIG. 7, thermoelectric heat generation would be targeted to
reduce the vehicle's fuel consumption and CO2 emission. In such an
example, generation elements may be proximate a cold-side heat exchanger
1050 and coolant flow may run in an axial direction in a cooling circuit
near a surface of the cold-side heat exchanger, and the cooling circuit
may be in thermal communication with the thermoelectric generator module.
Heat is then extracted from the after-treatment device at the location of
the thermoelectric generator at a rate and level which is given by the
rate and level the exhaust gas is supplying heat, by the thermal
conductivity of the filter or substrate, the thermoelectric generator and
the heat exchangers.

[0047] In embodiments, the thermoelectric generation elements may be
configured to cool the substrate. In embodiments, for example, coolant
flow adjacent to, or through circuits within, the thermoelectric
generation elements may be used to control the thermoelectric generator
in response to the temperature of the substrate. For example, in
embodiments, an after-treatment device may further comprise at least one
temperature sensor that may be configured to measure a temperature of the
interior volume, and the coolant flow may be adjusted (increased or
decreased) in response to the measured temperature. In embodiments, for
example, the coolant flow may be adjusted in response to a regeneration
event associated with a particulate filter substrate. In various
additional embodiments, the coolant flow in the catalytic convertor may
be adjusted to preserve a threshold temperature for the catalytic
activity. In still further embodiments, to auto-regulate the amount of
heat pulled from the substrate, a thermoelectric material with a steep
step function in its ZT performance with temperature can optionally be
applied to allow for a threshold response.

[0048] A number of approaches may be used to form the gaps within the
substrate or filter for the package of heat exchangers and TEG.
Cylindrical holes with some material cross-legs to ensure mechanical
stability of the substrate or filter may be formed while forming the
substrate or filter in an extrusion process with a suitable extrusion die
that is designed to provide the cylindrical gap space between two crowns
in the multicrown trough pattern in the size required for the heat
exchangers and thermoelectric generator. In other embodiments, the
substrate or filter may be formed and the cylindrical hole may be drilled
into the formed substrate.

[0049] In further embodiments, the heat exchangers and/or coolant channels
may also be directly formed by extrusion together with the substrate or
filter. For example, a heat exchanger of cylindrical geometry with or
without fins may be formed by extrusion. A coolant channel with a gap for
coolant to flow can also be extruded.

[0050] The thermoelectric generator efficiency (i.e., its extraction of
heat from the DPF, GPF, or catalytic converter) may be controlled and
changed over wide ranges by the flow rate of the coolant through the
cooling circuit. Thus, DPF, GPF, or substrate operation feedback may be
used, and based on the measured temperature, the coolant flow rate may be
adjusted. The adjustment may be made, for example, by a valve or
automated controller, as would be understood. A thermoelectric generator
could regulate temperature in a DPF, GPF, or catalytic converter, such as
by controlling the flow of a coolant as discussed above. With such
technology, high soot mass limits may be met for very high porosity parts
or for thin-walled parts. This design may allow cordierite and aluminum
titanate DPF to compete with high conductivity SiC filters.

[0051] As illustrated in FIG. 10 and also with reference to elements in
FIGS. 6 and 8, in embodiments, an after-treatment device, such as the
after-treatment device 100 in FIG. 6, may further comprise a housing,
such as, for example, an exhaust gas container 130 that contains the
substrate 106. Accordingly, in embodiments, when the substrate 106 is
housed within the container 130, thermoelectric generation elements 109
(e.g., comprising the thermoelectric generator 105) of FIG. 8 are
disposed entirely within the container 130. Thus, to reach the
thermoelectric generator 106, as shown in FIG. 10, connections within an
inlet fitting 131 and an outlet fitting 132 may breach the container 130
radially, or at an inlet 140 and/or outlet 141 of the container 130. The
inlet fitting 131 may comprise, for example, a coolant inlet tube 133, a
wire 134 for current in and control wiring 135 (if needed), and the
outlet fitting 132 may comprise a coolant outlet tube 136 and a wire 137
for current out. In embodiments, wires 134, 135 and 137 may be thermally
and electrically insulated using the fittings 131 and 132.

[0052] As those of ordinary skill in the art would understand, for
embodiments with multiple cylindrical channels, multiple fittings may be
used, with the possibility of manifold inlets and/or outlets.

[0053] In various additional exemplary embodiments, the disclosure relates
to methods for treating exhaust gas using the after-treatment devices
described herein, such as, for example, using the after-treatment device
of FIG. 7. More specifically, a method for dispensing exhaust gas may
comprise flowing the exhaust gas through a trough filter with an
integrated thermoelectric generator 1000. The exhaust gas may be flowed
through multiple concentric troughs 1010 and 1020 and through an annular
exhaust gas outlet channel between one or more of the multiple concentric
troughs 1010 and 1020. The exhaust gas may also be flowed through
thermoelectric generator 1040 positioned in thermal communication with
the annular exhaust gas outlet channel.

[0054] Depending on a particular application, in various embodiments, the
method may further comprise reacting the flowing exhaust gas with a
catalyst incorporated within the substrate 106, or filtering the flowing
exhaust gas within the substrate 106.

[0055] For the purposes of describing and defining the present invention
it is noted that the terms "substantially" and "about" are utilized
herein to represent the inherent degree of uncertainty that may be
attributed to any quantitative comparison, value, measurement, or other
representation. The terms "substantially" and "about" are also utilized
herein to represent the degree by which a quantitative representation may
vary from a stated reference without resulting in a change in the basic
function of the subject matter at issue.

[0056] It is noted that terms like "commonly" when utilized herein, are
not utilized to limit the scope of the claimed invention or to imply that
certain features are critical, essential, or even important to the
structure or function of the claimed invention. Rather, these terms are
merely intended to identify particular aspects of an embodiment of the
present disclosure or to emphasize alternative or additional features
that may or may not be utilized in a particular embodiment of the present
disclosure.

[0057] Having described the subject matter of the present disclosure in
detail and by reference to specific embodiments thereof, it is noted that
the various details disclosed herein should not be taken to imply that
these details relate to elements that are essential components of the
various embodiments described herein, even in cases where a particular
element is illustrated in each of the drawings that accompany the present
description. Rather, the claims appended hereto should be taken as the
sole representation of the breadth of the present disclosure and the
corresponding scope of the various embodiments described herein. Further,
it will be apparent that modifications and variations are possible
without departing from the scope of the appended claims.